using System;
using System.Collections.Generic;
using System.Text;
using SQLiteParser;
namespace SQLiteTurbo
{
/// <summary>
/// This class is responsible to generate change scripts that can be
/// used to migrate from one version of a database to another.
/// </summary>
public class ChangeScriptBuilder
{
#region Constructors
#endregion
#region Public Methods
/// <summary>
/// Generate a change script needed to migrate from the left database to the right database object
/// </summary>
/// <returns></returns>
public static string Generate(
string leftdb,
string rightdb,
Dictionary<SchemaObject, Dictionary<string, SQLiteDdlStatement>> leftSchema,
Dictionary<SchemaObject, Dictionary<string, SQLiteDdlStatement>> rightSchema,
Dictionary<SchemaObject, List<SchemaComparisonItem>> comp, ChangeDirection direction)
{
StringBuilder sb = new StringBuilder();
// Do everything within a transaction
sb.Append("-- Generated by SQLite Compare utility\r\n\r\n");
if (direction == ChangeDirection.LeftToRight)
sb.Append("-- The script can be used to migrate database\r\n-- " + leftdb + " schema\r\n-- to the schema of database\r\n-- " + rightdb + "\r\n\r\n");
else
sb.Append("-- The script can be used to migrate database\r\n-- " + rightdb + " schema\r\n-- to the schema of database\r\n-- " + leftdb + "\r\n\r\n");
sb.Append("BEGIN TRANSACTION;\r\n\r\n");
// There are 4 different types of objects that can be migrated:
// 1. Tables
// 2. Indexes
// 3. Triggers
// 4. Views
// Indexes depend on their tables so we can handle them only after handling the
// respective tables. Triggers depend on the associated table or view. If a trigger
// depends on a table - we can handle it only after handling the related table. If
// a trigger depends on a view - we can handle it only after handling the view.
// A view depends on one or more tables, but, unlike other objects - we can simply drop
// it and re-create it from scratch without damaging any data or schema information.
// We'll start by handling the hardest part first - tables
List<SchemaComparisonItem> tables = comp[SchemaObject.Table];
foreach (SchemaComparisonItem item in tables)
{
if (item.Result != ComparisonResult.Same)
{
string script = GenerateTableChangeScript(item, comp, direction, leftSchema, rightSchema);
sb.Append(script);
}
else
{
// The table itself did not change, but we still need to check its indexes and triggers
if (direction == ChangeDirection.LeftToRight)
ApplyIndexOrTriggerChanges(sb, item.LeftDdlStatement, leftSchema, rightSchema);
else
ApplyIndexOrTriggerChanges(sb, item.RightDdlStatement, rightSchema, leftSchema);
} // else
} // foreach
// Note: as part of creating a change script for a table object - we'll also
// generate change script for its related indexes and triggers so they
// don't require a separate handling here.
// We'll finish my handling views
List<SchemaComparisonItem> views = comp[SchemaObject.View];
foreach (SchemaComparisonItem item in views)
{
if (item.Result != ComparisonResult.Same)
{
string script = GenerateViewChangeScript(item, direction);
sb.Append(script);
}
else
{
// The view itself did not change, but we still need to check its triggers
if (direction == ChangeDirection.LeftToRight)
ApplyIndexOrTriggerChanges(sb, item.LeftDdlStatement, leftSchema, rightSchema);
else
ApplyIndexOrTriggerChanges(sb, item.RightDdlStatement, rightSchema, leftSchema);
}
} // foreachs
// Commit the transaction
sb.Append("\r\nCOMMIT TRANSACTION;\r\n");
return sb.ToString();
}
#endregion
#region Private Methods
private static string GenerateViewChangeScript(SchemaComparisonItem item,
ChangeDirection direction)
{
StringBuilder sb = new StringBuilder();
if (item.Result == ComparisonResult.ExistsInLeftDB)
{
if (direction == ChangeDirection.LeftToRight)
DeleteView(sb, item.LeftDdlStatement);
else
CopyView(sb, item.LeftDdlStatement);
}
else if (item.Result == ComparisonResult.ExistsInRightDB)
{
if (direction == ChangeDirection.LeftToRight)
CopyView(sb, item.RightDdlStatement);
else
DeleteView(sb, item.RightDdlStatement);
}
else if (item.Result == ComparisonResult.DifferentSchema)
{
if (direction == ChangeDirection.LeftToRight)
CopyView(sb, item.RightDdlStatement);
else
CopyView(sb, item.LeftDdlStatement);
} // else
return sb.ToString();
}
private static void DeleteView(StringBuilder sb, SQLiteDdlStatement stmt)
{
sb.Append("\r\n-- Deleting view " + stmt.ObjectName.ToString() + " from the updated schema\r\n\r\n");
sb.Append("DROP VIEW IF EXISTS " + stmt.ObjectName.ToString() + ";\r\n");
}
private static void CopyView(StringBuilder sb, SQLiteDdlStatement stmt)
{
sb.Append("\r\n-- Creating view " + stmt.ObjectName.ToString() + " from scratch\r\n\r\n");
sb.Append("DROP VIEW IF EXISTS " + stmt.ObjectName.ToString() + ";\r\n");
sb.Append(stmt.ToString() + ";\r\n");
}
private static string GenerateTableChangeScript(SchemaComparisonItem item,
Dictionary<SchemaObject, List<SchemaComparisonItem>> comp, ChangeDirection direction,
Dictionary<SchemaObject, Dictionary<string, SQLiteDdlStatement>> leftSchema,
Dictionary<SchemaObject, Dictionary<string, SQLiteDdlStatement>> rightSchema)
{
StringBuilder sb = new StringBuilder();
if (item.Result == ComparisonResult.ExistsInLeftDB)
{
if (direction == ChangeDirection.LeftToRight)
DeleteTable(sb, item.LeftDdlStatement);
else
CopyTable(sb, item.LeftDdlStatement, leftSchema);
}
else if (item.Result == ComparisonResult.ExistsInRightDB)
{
if (direction == ChangeDirection.RightToLeft)
DeleteTable(sb, item.RightDdlStatement);
else
CopyTable(sb, item.RightDdlStatement, rightSchema);
}
else if (item.Result == ComparisonResult.DifferentSchema)
{
if (direction == ChangeDirection.LeftToRight)
MigrateTable(sb, item.RightDdlStatement, leftSchema, rightSchema);
else
MigrateTable(sb, item.LeftDdlStatement, rightSchema, leftSchema);
}
return sb.ToString();
}
/// <summary>
/// Create the SQL code that is necessary to migrate an existing table to its
/// updated schema.
/// </summary>
/// <param name="sb">The string builder to which the code will be added</param>
/// <param name="stmt">The updated table schema object</param>
/// <param name="srcSchema">The source schema</param>
/// <param name="dstSchema">The destination schema</param>
private static void MigrateTable(StringBuilder sb, SQLiteDdlStatement stmt,
Dictionary<SchemaObject, Dictionary<string, SQLiteDdlStatement>> srcSchema,
Dictionary<SchemaObject, Dictionary<string, SQLiteDdlStatement>> dstSchema)
{
List<SQLiteColumnStatement> added = null;
SQLiteDdlStatement orig = srcSchema[SchemaObject.Table][SQLiteParser.Utils.Chop(stmt.ObjectName.ToString()).ToLower()];
if (Utils.AlterTableIsPossible(orig, stmt, ref added))
{
sb.Append("\r\n-- Adding missing table columns\r\n\r\n");
// In this case we can migrate the table by doing ALTER TABLE ADD COLUMN commands
foreach (SQLiteColumnStatement col in added)
{
sb.Append("ALTER TABLE " + stmt.ObjectName.ToString() + " ADD COLUMN " + col.ToString() + ";\r\n");
} // foreach
// If there are any differences in indexes or triggers - apply them now
ApplyIndexOrTriggerChanges(sb, stmt, srcSchema, dstSchema);
}
else
{
// In this case we need to re-build the table from scratch in order to "change" it.
sb.Append("\r\n-- Creating table "+stmt.ObjectName.ToString()+" from scratch (simple ALTER TABLE is not enough)\r\n\r\n");
// Create a table with the correct schema but with a temporary name
string tmpname = Utils.GetTempName(stmt.ObjectName.ToString());
SQLiteCreateTableStatement updTable = (SQLiteCreateTableStatement)stmt;
sb.Append(updTable.ToStatement(tmpname) + ";\r\n");
// Get the original table schema object
SQLiteCreateTableStatement origTable = (SQLiteCreateTableStatement)orig;
// Compute the set of common columns to the updated table schema and the original
// table schema
List<SQLiteColumnStatement> diffcols = null;
List<SQLiteColumnStatement> common = Utils.GetCommonColumns(origTable, updTable, false, out diffcols);
// Copy data rows from the original table to the temporary table
if (common.Count > 0)
{
// Check if all the columns that belong solely to the updated table schema (and are not
// common with the original table schema) supports NULL values or have DEFAULT values.
bool error = false;
List<SQLiteColumnStatement> ncols = new List<SQLiteColumnStatement>();
foreach (SQLiteColumnStatement c in updTable.Columns)
{
if (!Utils.ColumnListContains(common, c))
ncols.Add(c);
} // foreach
foreach (SQLiteColumnStatement c in ncols)
{
if (c.IsNullable || c.HasNonNullConstDefault)
continue;
// This column will cause any attempt to insert data into the updated table
// schema to fail, so we'll issue a warning comment
error = true;
sb.Append("\r\n-- WARNING: Column " + c.ObjectName.ToString() + " in table " + updTable.ObjectName.ToString() + " is NOT NULL and doesn't have a non-null constant DEFAULT clause. " +
"\r\n-- This will cause any attempt to copy rows from the original table to the updated table to fail." +
"\r\n-- No rows will be copied from the original table to the updated table!");
sb.Append("\r\n");
} // foreach
// Build a select columns list
string selectlist = Utils.BuildColumnsString(common, false);
// Build a select column list for those columns that belong exclusively to the updated table
// schema and that are nullable or have non-null DEFAULT clause.
string extralist = string.Empty;
if (ncols.Count > 0)
extralist = "," + Utils.BuildNullableOrNonNullConstantDefaultSelectList(ncols);
// Compute the list of all columns that are common to both tables and those that exist only in the
// updated table but are nullable or have non-null constant default.
string allCols = null;
if (common.Count > 0)
{
if (ncols.Count > 0)
allCols = selectlist + "," + Utils.BuildColumnsString(ncols, false);
else
allCols = selectlist;
}
else
allCols = Utils.BuildColumnsString(ncols, false);
if (!error)
{
// Now copy only the columns that can be transferred from the original table
sb.Append("\r\n-- Copying rows from original table to the new table\r\n\r\n");
sb.Append("INSERT INTO " + tmpname + " ("+allCols+")"+
" SELECT " + selectlist + extralist+" FROM " + origTable.ObjectName.ToString() + ";\r\n");
} // if
} // if
// Drop the original table and rename the temporary table to have the name of the original table
sb.Append("\r\n-- Droping the original table and renaming the temporary table\r\n\r\n");
sb.Append("DROP TABLE " + origTable.ObjectName.ToString() + ";\r\n");
sb.Append("ALTER TABLE " + tmpname + " RENAME TO " + origTable.ObjectName.ToString() + ";\r\n");
// Re-create all indexes of the updated table
bool found = false;
foreach (SQLiteCreateIndexStatement cindex in dstSchema[SchemaObject.Index].Values)
{
if (SQLiteParser.Utils.Chop(cindex.OnTable).ToLower() ==
SQLiteParser.Utils.Chop(updTable.ObjectName.ToString()).ToLower())
{
if (!found)
{
sb.Append("\r\n-- Creating associated indexes from scratch\r\n\r\n");
found = true;
}
sb.Append(cindex.ToString() + ";\r\n");
}
} // foreach
// Re-create all triggers of the updated table
found = false;
foreach (SQLiteCreateTriggerStatement trg in dstSchema[SchemaObject.Trigger].Values)
{
if (trg.TableName.Equals(updTable.ObjectName))
{
if (!found)
{
sb.Append("\r\n-- Creating associated triggers from scratch\r\n\r\n");
found = true;
}
sb.Append(trg.ToString() + ";\r\n");
}
} // foreach
} // else
}
private static void ApplyIndexOrTriggerChanges(StringBuilder sb, SQLiteDdlStatement stmt,
Dictionary<SchemaObject, Dictionary<string, SQLiteDdlStatement>> srcSchema,
Dictionary<SchemaObject, Dictionary<string, SQLiteDdlStatement>> dstSchema)
{
// If there are any differences in indexes - apply them now
List<SQLiteCreateIndexStatement> changedIndexes = null;
List<SQLiteObjectName> removedIndexes = null;
if (Utils.TableIndexesWereChanged(stmt.ObjectName.ToString(), srcSchema[SchemaObject.Index], dstSchema[SchemaObject.Index],
out changedIndexes, out removedIndexes))
{
foreach (SQLiteObjectName iname in removedIndexes)
sb.Append("DROP INDEX IF EXISTS " + iname.ToString() + ";\r\n");
foreach (SQLiteCreateIndexStatement idx in changedIndexes)
{
sb.Append("DROP INDEX IF EXISTS " + idx.ObjectName.ToString() + ";\r\n");
sb.Append(idx.ToString() + ";\r\n");
} // foreach
}
// If there are any differences in triggers - apply them now
List<SQLiteCreateTriggerStatement> changedTriggers = null;
List<SQLiteObjectName> removedTriggers = null;
if (Utils.TableTriggersWereChanged(stmt.ObjectName.ToString(), srcSchema[SchemaObject.Trigger], dstSchema[SchemaObject.Trigger],
out changedTriggers, out removedTriggers))
{
foreach (SQLiteObjectName iname in removedTriggers)
sb.Append("DROP TRIGGER IF EXISTS " + iname.ToString() + ";\r\n");
foreach (SQLiteCreateTriggerStatement trg in changedTriggers)
{
sb.Append("DROP TRIGGER IF EXISTS " + trg.ObjectName.ToString() + ";\r\n");
sb.Append(trg.ToString() + ";\r\n");
} // foreach
} // if
}
/// <summary>
/// appends the SQL commands needed to delete a table from the target database
/// </summary>
/// <param name="sb">The string builder objcet</param>
/// <param name="stmt">The table statement schema objcet</param>
private static void DeleteTable(StringBuilder sb, SQLiteDdlStatement stmt)
{
string tableName = stmt.ObjectName.ToString();
sb.Append("\r\nDROP TABLE " + tableName + ";\r\n");
}
/// <summary>
/// Append the SQL commands needed to copy a table from a source database to
/// the target database.
/// </summary>
/// <param name="sb">The string builder object</param>
/// <param name="stmt">The CREATE TABLE schema object</param>
/// <param name="srcSchema">The source schema from which the table is copied</param>
private static void CopyTable(StringBuilder sb, SQLiteDdlStatement stmt,
Dictionary<SchemaObject, Dictionary<string, SQLiteDdlStatement>> srcSchema)
{
string tableName = stmt.ObjectName.ToString();
// The table (and any associated triggers and/or indexes) does not exist in the
// right database, so we need to create it from scratch.
string create = stmt.ToString();
sb.Append("\r\n"+create + ";\r\n");
// Create any associated indexes
Dictionary<string, SQLiteDdlStatement> indexes = srcSchema[SchemaObject.Index];
foreach (SQLiteCreateIndexStatement cindex in indexes.Values)
{
if (SQLiteParser.Utils.Chop(cindex.OnTable).ToLower() ==
SQLiteParser.Utils.Chop(tableName).ToLower())
{
sb.Append(cindex.ToString() + ";\r\n");
}
} // foreach
// Now add CREATE for any triggers of this table
Dictionary<string, SQLiteDdlStatement> triggers = srcSchema[SchemaObject.Trigger];
foreach (SQLiteCreateTriggerStatement ctrig in triggers.Values)
{
if (SQLiteParser.Utils.Chop(ctrig.TableName.ToString()).ToLower() ==
SQLiteParser.Utils.Chop(tableName).ToLower())
{
sb.Append(ctrig.ToString() + ";\r\n");
}
} // foreach
}
#endregion
}
public enum ChangeDirection
{
None = 0,
LeftToRight = 1,
RightToLeft = 2,
}
}